Overall Rationale for the Resource The overall rationale for the National Resource for the Mass Spectrometric Analysis of Biological Macromolecules is to develop instrumentation and methodology that facilitates biological and biomedical research; test and apply these developments on important problems of biomedical interest; disseminate our developments to the biomedical community at large; and train scientists in these advanced techniques. Our goal is to push the envelope in terms of sensitivity, accuracy and breadth of application, so that mass spectrometry can be applied more and more broadly for uncovering new biology and become an increasingly important facilitator of biomedical research.